DSD-INT 2015 - identification of mixing zones in the EU – a tiered approach - dju bijstra, rijkswaterstaat & frank kleissen,

identification of mixing zones in the EU

1. Experiences with
mixing zones in the
Netherlands





Dju Bijstra (RWS)
Frank Kleissen (Deltares)
Christophe Thiange (Deltares)

2. Rijkswaterstaat
2 Experiences in with mixing zones in
the Netherlands
RWS UNCLASS
Contents
•Context

•Discharge test

•Tiered approach

•developments of the discharge test

3. Rijkswaterstaat
3 Experiences in with mixing zones in
the Netherlands
RWS UNCLASS
Why using the discharge test?
•WFD objectives
- Good ecological status (2027)
- Good chemical status (2027)

• Insight in relation (point)sources and waterquality is necessary

4. Rijkswaterstaat
4 Experiences in with mixing zones in
the Netherlands
RWS UNCLASS
Mixing zones: why used and restricted?
• where two watercourses join there is a mixing zone
• difference in flow
• difference in concentration
• as long as C
discharge > C
surface water there is a mixing zone
• as long as C
discharge > EQS there is an area of exceedance
C > EQS
Mixing zones are inevitable

5. Rijkswaterstaat
5 Experiences in with mixing zones in
the Netherlands
RWS UNCLASS
x L
MAC-mixing zone:
(acute effects)
EQS-mixing zone:
(chronic effects)
Because of the ecological significance
of (river)banks concentration at the
bank is calculated and used as a starting
point for the assessment
Length
MAC-mixing zone (X
mac)
:
0,25*Width (max 25 m)
Length
EQS-mixing zone (X
L):
10*Width (max 1000 m)
Mixing zone
For calculating the dimensions of a
mixing zone an application “the
discharge test” has been
develloped.

6. Rijkswaterstaat
6 Experiences in with mixing zones in
the Netherlands
RWS UNCLASS November 20, 2015
Starting points: discharge test
Fast and easy
Little info needed
EXPERT DETAILED RESEARCH Time consuming
Lots of data needed
sieve
Worst case (low flow) conditions:
Q90 and max. load
Inert behaviour substances
Non problems
Potential problems Complex modelling

7. Rijkswaterstaat
7 Experiences in with mixing zones in
the Netherlands
RWS UNCLASS
Experiences with the discharge test in the Netherlands
•The discharge test has been developed in the Netherlands in 2000

•Assessment with discharge test is required for a permit

•Most discharges can the meet the criteria

•In 2011 the EU-guidance on mixing zones was adopted

•In 2011 the NL-discharge test has been adapted to this guidance

8. Rijkswaterstaat
8 Experiences in with mixing zones in
the Netherlands
RWS UNCLASS
Tiered Approach (1)
•TIER 0: Are (prioritary) substances present in the discharge in
concentrations >EQS? NO  Stop

•TIER 1: is the discharge significant? NO  Stop



Yes

9. Rijkswaterstaat
9 Experiences in with mixing zones in
the Netherlands
RWS UNCLASS
Tier 1: Significancetest
Stop
Yes
Is C
complete mixing significant?
Attention!:
For discharges at sea and lakes with a width
> 2000 m and harbours the siginifance test can NOT
be applied!

10. Rijkswaterstaat
10 Experiences in with mixing zones in
the Netherlands
RWS UNCLASS
watersystem width [m] Allowed (trivial) increase in
concentration (% EQS)
(after complete mixing)
fresh waters and tidal rivers
*)

Small ≤ 100 1
Middle 100 < width ≤ 400 0,75
large > 400 0,1
Canals
all all 1
Can criteria in
table be met?
Stop
Yes
Is C
complete mixing significant?
Tier 1: Significancetest

11. Rijkswaterstaat
11 Experiences in with mixing zones in
the Netherlands
RWS UNCLASS
Tiered Approach (2)
•TIER 0: Are (prioritary) substances present in the discharge in
concentrations >EQS? NO  Stop

•TIER 1: is the discharge significant? NO  Stop

•TIER 2: determination of mixing-zone whith the discharge-test:
are dimensions of MAC-MZ and/or EQS-MZ
bigger than criteria proposed? NO  Stop


Yes
Yes

12. Rijkswaterstaat
12 Experiences in with mixing zones in
the Netherlands
RWS UNCLASS
Tiered Approach (2)
•TIER 0: Are (prioritary) substances present in the discharge in
concentrations >EQS? NO  Stop

•TIER 1: is the discharge significant? NO  Stop

•TIER 2: determination of mixing-zone whith the discharge-test:
are dimensions of MAC-MZ and/or EQS-MZ
bigger than criteria proposed? NO  Stop

•TIER 3: Complex modelling: Is MZ a problem? NO  Stop

•TIER 4: Local (effect)assessment (i.e. bioassays) (optional):
Is MZ a problem? NO  Stop


Yes
Yes
Yes
Yes
measures or
or measures
measures Yes
If necessary new complex modelling

13. Rijkswaterstaat
13 Experiences in with mixing zones in
the Netherlands
RWS UNCLASS
Modeling tools for Tier 2
•Excell discharge test (fresh (streaming) waters)
(simple and the amount of input data needed is limited)

•Web-based application (fresh waters; harbours; tidal waters)
(more input data are needed)

•http://apps.helpdeskwater.nl/prog/extra/immissietoets/sources/#ver
sion=nl-nl

14. Rijkswaterstaat
14 Experiences in with mixing zones in
the Netherlands
RWS UNCLASS
Developments of the
discharge test
Discharge test 2000
(spreadsheet)
New tools 2011:
Webbased application and
spreadsheet
WFD and guidance on mixing
zones
Complexity of tidal waters
Database with Water-
system parameters
User experiences
New tools 2015:
New environment for
Webbased application
Database with water
quality data
Database with water
quality standards

15. Rijkswaterstaat
15 Experiences in with mixing zones in
the Netherlands
RWS UNCLASS
April 2011
How it works



•Based on a combination of mixing factors:
–Backgroundmixing
–Additional plume/jet mixing:

•Substances not affected by processes other than mixing

•The calculations depend on the type of receiving water

16. Rijkswaterstaat
16 Experiences in with mixing zones in
the Netherlands
RWS UNCLASS April 2011
Rivers/Canals
No density difference: plume calculation using Fisher’s description
With density difference: jet calculations using jet3D (3-dimensional)

17. Rijkswaterstaat
17 Experiences in with mixing zones in
the Netherlands
RWS UNCLASS
April 2011
Harbours
Concentration resulting from:
Exchange harbour and main water body and plume/jet

Exchange of water
between harbour and
main waterbody due to:
• Tidal exchange,
• eddies,
• density difference.

In addition optional other
discharge

18. Rijkswaterstaat
18 Experiences in with mixing zones in
the Netherlands
RWS UNCLASS
Tracer simulations
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19. Rijkswaterstaat
19 Experiences in with mixing zones in
the Netherlands
RWS UNCLASS
Waterbody properties from database
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20. Rijkswaterstaat
20 Experiences in with mixing zones in
the Netherlands
RWS UNCLASS


















Questions?
•Thank you for your attention!










Workshop 4 pm in Room Ambition.

Questions ?